The statement "friction force is a contact force while magnetic force is a non-contact force" is
- A.always true.
- B.true only at 0°C.
- C.a false statement.
- D.either true or false depending upon the temperature of the surroundings.
Correct answer
Explanation
The correct answer is A, always true. Friction acts only where two surfaces touch, while a magnet can push or pull an object across a gap.
Forces are grouped by whether the bodies must touch. Contact forces, such as friction, muscular force, normal reaction and tension, arise only from direct contact; friction comes from the tiny bumps on two surfaces catching on each other as they slide. Non-contact forces, such as magnetic, electrostatic and gravitational forces, act through a field, so a magnet lifts iron pins from a distance and the Earth pulls a falling apple. This classification depends on how the force acts, not on any outside condition.
B is wrong: nothing about the nature of these forces is tied to 0°C.
C is wrong: the statement describes both forces correctly.
D is wrong: temperature may change the size of a force, but not whether it needs contact.
Exam tip: non-contact forces are the field forces, namely gravitational, magnetic and electrostatic; friction, tension and muscular force need contact.
Practice Questions
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- B.diploid zygote
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- D.motile male gametes
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- B.Two
- C.Three
- D.Four
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- A.10⁻⁷ cm
- B.10⁻⁶ cm
- C.10⁻⁴ cm
- D.10⁻³ cm
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- A.CₙH₂ₙ₊₂
- B.CₙH₂ₙ₋₂
- C.CₙH₂ₙ₊₁
- D.CₙH₂ₙ₋₁
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- B.Malaria
- C.Smallpox
- D.Elephantiasis
Show answer
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